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Re: Julian Day Question [message #48881 is a reply to message #48880]

Thu, 25 May 2006 23:13

David Fanning
Messages: 11724
Registered: August 2001

Senior Member

David Fanning writes:

> Consider:
>
> IDL> Print, JULDAY(1, 1, 1999) ; 1 Jan 1999
> 2451180
>
> This is the wrong answer according to Meeus, who lists the
> answer as 2451179.5.
>
> But, then consider this, which should be the SAME time:
>
> IDL> Print, JULDAY(1, 1, 1999, 0) ; 1 Jan 1999 at 0 hours
> 2451179.5
>
> What do you make of that?

Here is the same thing, but with JHUAPL routines:

IDL> Print, YMD2JD(1999, 1, 1)
2451180

But, converting first to "Julian seconds", and then to the Julian
Day:

IDL> js = YMDS2JS(1999, 1, 1, 0)
IDL> Print, JS2JD(js)
2451179.5

Clearly, I am missing something important here. :-(

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/

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[Message index]

		Re: Julian Day Question By: David Fanning on Tue, 30 May 2006 16:02
		Re: Julian Day Question By: Mark Hadfield on Tue, 30 May 2006 15:46
		Re: Julian Day Question By: Mark Hadfield on Tue, 30 May 2006 15:42
		Re: Julian Day Question By: David Fanning on Fri, 26 May 2006 12:31
		Re: Julian Day Question By: K. Bowman on Fri, 26 May 2006 11:30
		Re: Julian Day Question By: Paul Van Delst[1] on Fri, 26 May 2006 10:09
		Re: Julian Day Question By: news.qwest.net on Fri, 26 May 2006 10:05
		Re: Julian Day Question By: news.verizon.net on Fri, 26 May 2006 09:57
		Re: Julian Day Question By: news.qwest.net on Fri, 26 May 2006 09:53
		Re: Julian Day Question By: Paul Van Delst[1] on Fri, 26 May 2006 09:43
		Re: Julian Day Question By: James Kuyper on Fri, 26 May 2006 09:20
		Re: Julian Day Question By: Paul Van Delst[1] on Fri, 26 May 2006 07:20
		Re: Julian Day Question By: David Fanning on Fri, 26 May 2006 07:17
		Re: Julian Day Question By: Mike Wallace on Fri, 26 May 2006 07:05
		Re: Julian Day Question By: Greg Hennessy on Fri, 26 May 2006 04:40
		Re: Julian Day Question By: David Fanning on Thu, 25 May 2006 23:48
		Re: Julian Day Question By: David Fanning on Thu, 25 May 2006 23:28
		Re: Julian Day Question By: David Fanning on Thu, 25 May 2006 23:21
		Re: Julian Day Question By: Craig Markwardt on Thu, 25 May 2006 22:52
		Re: Julian Day Question By: David Fanning on Thu, 25 May 2006 23:13
		Re: Julian Day Question By: David Fanning on Thu, 25 May 2006 23:03
		Re: Julian Day Question By: Mike Wallace on Thu, 25 May 2006 22:27
		Re: Julian Day Question By: Paul Van Delst[1] on Fri, 02 June 2006 10:03

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